Mercedes-Benz Hybrid Vehicle – No Start Problem
Mercedes-Benz hybrid vehicles such as the S400 are notorious for having hybrid issues that lead to no-start engine conditions. The most common Mercedes-Benz hybrid problems that won’t allow you to start the engine are caused by either a faulty power electronic module (part number 0009064703) or a defective hybrid battery.
- Most Common Causes: Power Module (60%), Hybrid Battery (40%)
- Repair Difficulty: Professional Only
- Safety Warning: High Voltage System
At the time of this article, we diagnosed many Mercedes-Benz S400 vehicles with no-start problems. We found that 60% of them wouldn’t start due to the failure of the Power Electronics module, and the other 40% would not start due to the failure of the high-voltage hybrid battery. It is important to run a full system scan and get a report of all the STORED and CURRENT fault codes to find out why an S400 won’t start.
Symptoms
Symptoms of a faulty power electronic module on a Mercedes-Benz S400 Hybrid:
🔧 Stop paying the dealer for every warning light
Get dealer level diagnostics at home with the YOUCANIC Full System Scanner.
- ✔ Works with all makes and models, including most luxury brands
- ✔ Topology map view shows all vehicle modules on one screen for faster diagnostics
- ✔ Bi directional controls to test fans, pumps, actuators and more so you do not have to guess
- ✔ Special resets and calibrations such as ABS bleed, EPB service, battery registration and more
- ✔ Free lifetime updates with no recurring fees
- The vehicle won’t start.
- Vehicle starts intermittently
- The dash lights and ignition turn on, but the car won’t start.
Required Tools Section
To properly diagnose Mercedes hybrid issues, you’ll need:
– Professional-grade scanner with Mercedes-specific capabilities
– Ability to read factory codes (not just generic P-codes)
– High-voltage safety equipment
You will need a pro scanner, such as the YOUCANIC Full System Scanner, to diagnose Mercedes-Benz hybrid problems.
Power Electronics Module
Based on the YOUCANIC team’s experience, the most common problem with the Mercedes-Benz S400 Hybrid is the power electronic module (sometimes called a power inverter).
This module’s function is to receive commands from a hybrid ECM via the CAN-BUS Network and control inverter energy flow to and from the battery and engine. It can also control the speed and timing of an electric motor in unison with an Internal combustion engine. It also controls and monitors other components, such as batteries, charging, and related modules.
The power electronic module should not be confused with the DC/DC converter. 
The power electronic module is mounted on the side of the engine/transmission, below the right exhaust manifold, and on the passenger side.
The three-phase electrical connector melts, which means you can no longer start the engine since the electrical motor is used for starting. Remember that the S400 hybrid has no starter; instead, it uses the electric motor mounted in front of the torque converter.
Replacing the Power Electronic Moule at a Mercedes-Benz dealership costs between $10,500 and $12,000. This repair can be done at a fraction of that cost by our team or an independent repair shop. For more help, see How to replace the Mercedes-Benz Power Electronic module.
The good news is that a used or refurbished power electronic unit does not need to be programmed. After the repair, fault codes must be cleared with a Mercedes-Benz scanner.
The fault codes will be stored in Power Electronic Module (SG-EM) and Engine Control Unit (ECU):
- U011000 – Communication with control unit Electric machine A has a malfunction.
- U011081 – Communication with control unit Electric machine A has a malfunction. Incorrect data were received.
A faulty power electronic module triggers these codes. You can buy a refurbished power electronic module (0009064703) online.
The following part numbers are often associated with the power electronic module.
- 0009064703 / 0009065802 / A0009065802
- A 000 906 58 02, 0005844147 / A0005844147
- A 000 584 41 47, 2213430400 / A2213430400,
- 2213430300 / A2213430300, A2213431100,
- 2213430900 / A2213430900, 2213430500,
- 2213400400 / A2213400400, 2213400300
- A2213400300, 2213400600 / A2213400600
- 2213400500 / A221340050
Mercedes-Benz has issued a few different numbers for the power electronic module, as the unit has undergone multiple revisions.
Other reasons why your S400 Hybrid may not start include:
- Hybrid battery failure is a widespread failure.
- Faulty inverter – The inverter is located behind the right side fender. It is not a common issue.
- Faulty A/C compressor – Common
To find out why your S400 Hybrid won’t start, you must read the Battery Management System module’s fault codes. It is also essential to run a full system scan to determine fault codes in other modules. An S400 may also not start for other reasons, sometimes unrelated to the hybrid system. For example, other reasons why a Mercedes-Benz S-Class won’t start include:
- Ignition Switch – EIS,
- Intelligent Servo Module – ISM,
- Engine Control Unit – ECU
- Weak or dead 12-volt battery.
- Stored fault codes that need to be cleared.
Let’s look at some of the most common issues we mentioned above.
Hybrid Battery
Another common problem with the Mercedes-Benz S400 Hybrid is the failure of the hybrid battery, explained in detail here.
Two (2) types of electrical systems are being implemented in a hybrid system. One is the 12-volt electrical system powered by a 12-volt onboard battery. The 12-volt system powers almost 90 percent of the car, including lights, entertainment, horn, etc.
The high-voltage electrical system is powered by a battery with>100 volts DC. A hybrid Battery, high Voltage, or HV battery, is the Hybrid electric motor’s powerhouse.
Its primary purpose is to power the Hybrid electric motor, which helps the Internal combustion engine with its load. It also acts as a starter for the Internal Combustion Engine. For an internal combustion engine to start, the HV battery should have a 15% charge. You can check the charge level via the command by going to System > Hybrid Charge.
Common fault codes that show up as stored or current in the battery management module (SG-BMS):
- 180F00 – The high-voltage battery malfunctioned during the recovery phase.
- 0BBD00 – The limit value for the difference between the high-voltage battery module cell voltages has been exceeded.
- 0BBE00 – The cell voltages in the high-voltage battery module are different.
- 0A7D00 – The charge level of the high-voltage battery module is low.
- 180C00, 180500 – The hardware monitoring function has detected a fault in the control unit.
- 0A1F04 – There is an internal fault in the control unit Battery. There is an internal fault.
- 0AE886 – The temperature sensor D of the high-voltage battery has an electrical fault. There is an incorrect signal.
- 0ACA86 – The temperature sensor C of the high-voltage battery has an electrical fault. There is an incorrect signal.
- 0AC586 – The temperature sensor B of the high-voltage battery has an electrical fault. There is an incorrect signal.
- 0A9B86 – The temperature sensor A of the high-voltage battery has an electrical fault. There is an incorrect signal.
- 0A1F96 – There is an internal fault in the control unit Battery. There is an internal component fault.
- 0A1F00 – There is an internal fault in the control unit Battery.
DC/DC Converter
Sometimes, the DC-to-DC converter goes bad, but this failure is infrequent. When it fails, it can not transfer 130 to 12 Volts and vice versa. Follow this guide to learn more about the Mercedes-Benz DC/DC converter and how to replace it.
A/C Compressor
Another problem with the S400 is a defective A/C compressor, preventing the engine from starting.
The AC compressor is the heart of the air conditioning system. In Internal Combustion engine cars, the engine can operate normally with a faulty AC compressor. In a Hybrid System, however, the refrigerant from the AC compressor’s refrigerant serves as a cooling mechanism for the battery.
A Hybrid AC Compressor is also operated by a high-voltage DC rather than a belt to a pulley on an Internal Combustion engine. The ECM protects the battery from overheating by monitoring the AC status and taking actions such as turning off the CAN-BUS communication when the problem is detected.
The AC compressor runs on high voltage, which is not belt-driven. There is a 60A inline fuse mounted on top of the transmission. The yellow cable runs from the hybrid battery to Power Electronic Module and AC compressor. The 60A fuse protects the AC compressor, not the Power Electronic module.
Service Campaign
It is important to note that Mercedes-Benz had issued a service campaign 2012080004, for this problem. We called to check with the dealer on several S400 Hybrids, and according to the service manager, the dealer performed the service for both cases.
The dealer verifies the part number. If the vehicle is equipped with the Power Electronics module’s early model, the dealer replaces it free of charge. Our S400 had the “newer” version of the power electronic module, so the dealer did not replace it. Yet, even the “newer” version of the power electronic module is still failing.
Because the Power Electronic module is mounted next to the exhaust manifold, the chances of the new unit failing eventually remain high.
How to diagnose a Mercedes-Benz Hybrid that doesn’t start?
- Plug the YOUCANIC scanner into the OBD2 port.
- Select the Mercedes-Benz model.
- Go to Control Units
- Read the fault codes from these modules.
– ME Motor Electrnoic ECU
– SG BMS (Battery Management System)
– Power Electronics Module
– DC/DC Control Unit - Send the fault codes to support@youcanic, and we can give you an idea of what is wrong.
Based on our experience, if the vehicle has between 50,000 and 80,000 miles, the most likely problem is the failure of the hybrid battery. If the vehicle has between 90,000 and 125,000 miles, then it is likely that the power electronic module has failed.
Further Troubleshooting
If you are having issues with the Hybrid, please “contact the YOUCANIC” team with any questions that you may have. We can help you troubleshoot the problem if you send us the codes. We need the codes from these four modules:
- Engine ECU,
- DC/DC converter,
- BMS,
- Power Electronics Module.
Once we have the codes, we can tell you if you have a bad power electronic module, hybrid battery, or both.
If your vehicle is at the dealership or mechanic, ask them for the list of codes and send them to us. If you want to ship the car to Baltimore, we can repair it at a fraction of the dealer’s cost. We love these cars and believe it is a sin to pay over $10k to keep them running.
Definition of Terms
- CAN-BUS – Control Area Network. It serves as a channel of communication between various control modules.
- DC- Direct Current (Energy from the battery measured in volts).
- ECM – Electronic Control Module (Main Control Module)
- EMCM – Power Electronic Module, Motor Controller Module, or Electric Motor ECU.
- HV – High Voltage
Frequently Asked Questions
Are there any common problems with the power electronic module?
Yes, burned-out circuit boards are the most common failures of these cars.
What are the common safety guidelines before working on a Hybrid Vehicle’s Power Electronic Module?
1. The power electronic module is equipped with three or more high-voltage capacitors, be sure to discharge capacitors to avoid electric shock.
2. You can discharge an HV capacitor by shorting its negative and positive leads using a screwdriver, or you can also use a high resistor with a high Ohm rating and a plier.
How to diagnose a burned or faulty power electronic module using a scanner?
Even if there is damage or burn to the board, the reader can access the module and determine the error.
1. Connect the scanner to the OBD port.
2. Use Electronic Motor Control Unit Menu to check for faults.
How to disable a high-voltage system?
You should disable the high voltage 120v System:
1. Locate the onboard 12 volts battery.
2. Disconnect the 12v onboard battery ground line.
3. Use a voltage tester to ensure no voltage is passing from the charging
4. point of the pre-fuse box and the ground.
5. This would ensure no transient voltage is stuck between the onboard and auxiliary batteries.
6, It would also ensure that the auxiliary battery does not continue to supply the vehicle.
7. Wear your protective equipment, including electric-resistant globes, an anti-arc jacket, and a helmet with a face shield.
8. You can disconnect the HV connection from the high-voltage battery module.
9. Safely stick tape on the HV connector and, as much as possible, label it with a warning.
10. You may now connect the onboard battery for diagnostic procedures.
What are the common problems of a DC-to-DC converter?
• DC-to-DC converters can have a blown fuse.
• It can have inverter failures that can cause a no-start.
• It can cause the battery not to charge.
How to diagnose a faulty DC-to-DC converter?
You can use the YOUCANIC Full System Scanner to get into various control systems, reset errors and carry out tests like Xentry Diagnostics.
What common problems with AC compressors could affect the Hybrid operation?
Any problem that would stop the AC from functioning, such as a blown fuse, is regarded by ECM as a severe error and would take out the CAN-BUS communication offline.
How would you know if the CAN-BUS communication is offline using a scanner?
1. Connect the scanner to the OBD2 port
2. Check the status of “Hybrid CAN-BUS” it should be in an On status if everything is working.
ECM will throw an Interlock circuit of the High Voltage On-Board Electrical System Has A Sporadic Malfunction error during maintenance since the HV system is disconnected.
ECM will throw the same error if the power electronic module connector is disconnected or the fuse on top of the transmission is blown.
Could you work on your Mercedes-Benz S-400 Hybrid on your own?
No. As explained in the sections above, there is a high risk of injuries due to electric shock from the High Voltage System. Based on this, we only recommend that trained mechanics work on the high-voltage hybrid system. Non-contact electric shock can also happen due to High voltage arc. Also, you must buy expensive safety gear before working on the S-400 Hybrid.
Thanks for reaching out. Check out your email and we will do what we can to help you out.
I have a no start problem with my 2010 Mercedes Benz S400 Hybrid. I like what you said ‘we love these cars and believe it is a sin to pay over $10k to keep them running’. that’s exactly what a local MB dealership is asking to repair mine and its insane!
I’ve contacted you via your contact us on your webs. Let me know how you can repair mine as soon as possible.